A. Field of the Invention
The present invention relates to the field of computer controlled display systems for use in a computer system. More particularly, the field of the invention relates to computer systems that include menus, such as pull-down menus, which are displayed on a video screen controlled by a computer system.
B. Prior Art Background
Many prior art computer systems include computer controlled display systems which utilize bit-mapped displays which typically present a graphic image to the user of the computer system. In these computer controlled display systems, a bit-mapped image appears on a display means, such as a cathode ray tube (CRT); the bit-mapped image is typically generated and stored in a frame buffer which acts as a memory for the display system. In these display systems, the user typically interacts with the computer system by manipulating a cursor control means, such as a mouse. The user uses the mouse to position a cursor on the bit-mapped image to select options which are displayed under the control of the computer system on the display means. An example of such a prior art computer system is the Macintosh series of computers produced and offered by Apple Computer, Inc. of Cupertino, California. An exemplary description of bit-mapped computer controlled display systems may be found in U.S. Pat. No. 4,622,545, which is assigned to the assignee of the instant invention.
A typical prior art computer controlled display system is described in U.S. Pat. No. 4,464,652, which has been reissued as U.S. Pat. No. Re. 32,632. In the display system described in that patent, a mouse is coupled to the computer display system to control selectively the position of a cursor on a display means, such as a computer screen simply by moving the mouse over a surface, such as a desk, until the desired cursor position is shown on the display screen. The display system described in U.S. Pat. No. Re. 32,632 includes a "pull-down" menu. The mouse described in that patent includes a switch means which is utilized with the positioning of the cursor on the screen to selectively display command items corresponding to a particular command option (sometimes referred to as a menu title) which appears along a menu bar on the screen (display means). The command items are displayed in a menu window which is typically immediately below the command option which has been selected. That command option is selected by placing the cursor on or near the command option and setting the switch on the mouse to a second position, thereby causing the menu window to be displayed. If the user wishes to make a selection of one of the items in the menu window, the user continues to drag the mouse and thereby the cursor, down the menu window until the cursor appears over or near the particular command item the user wishes to select. The user then releases the switch means to thereby set the switch in a first position, which instructs the computer to execute the command item selected.
While this prior art display system employing pull-down menus has met with considerable success, the pull-down menu which is produced by this method frequently obscures portions of the images on the display means when the user would like to see those portions (e.g. to determine what selection to make in the pull-down menu). That is, since the pull-down window generates a menu window which is typically in a fixed position, any images near that fixed position are frequently obscured by a menu window when it is generated by the foregoing techniques. Moreover, the menu window generated through these pull-down menu techniques is accessible only when a command option has been selected. In other words, the command items present in a particular menu window are not accessible until a command option has been selected.
The present invention provides an improved computer controlled display system in which the menu windows may be removed from the menu bar and positioned on the screen of the display means. Once the menu window has been removed from the menu bar, the menu window may be repositioned on the screen of the display means or may be closed and thereby removed from the screen.